This invention relates to filtering devices known as bag filters in which a series of tubular filter bags are positioned across a gas stream to intercept and collect the dust particles therein. As gas passes through the filter and dust particles continue to collect thereon, accumulations of dust must be periodically removed in order that the gas stream passing through the filter will not be retarded by excessive resistance to flow and optimum flow conditions may be maintained.
It is the usual practice to employ one of various rapping, shaking or oscillating devices in which a shaking motion produced by mechanical or pneumatic devices effectively jars the collected dust particles from the filter surface upon which they are deposited and allows them to fall to the bottom of a surrounding filter housing. Examples of this type device are represented by U.S. Pat. No. 3,550,358 of R. V. McCabe and U.S. Pat. No. 2,167,238 of G. A. Geisler.
A mechanical shaking device usually requires the use of an electric motor together with wear prone cams or other linkages to produce a shaking motion that is imparted to the filter bags. A pneumatic shaking device may obviate the usage of certain mechanical linkages, but it does require the use of a pump, motor and costly pneumatic lines so that such a device has equally undesirable attributes.